1 REFRACTION OF LIGHT THROUGH PLAN PARALLEL GLASS A. PURPOSE OF EXPERIMENT There are some purposes which want to be achieved from this experiment. 1. Determining the value of the index of refraction of plan parallel glass. 2. Determining the value of the shift between the coming light and light of refraction out of plan parallel glass. B. TOOLS AND MATERIALS Here are the tools and materials needed in order to do this experiment. 1. Box of Light (Ray Box) 2. Protractor (SSN = 1 o ) 3. Plan Parallel Glass 4. Pencil 5. Ruler (SSN = 0.1 cm) 6. HVS Paper (White Paper) C. FUNDAMENTAL THEORY Refraction of light is a phenomenon of the light propagation direction changing since the light passes the two different mediums. The refraction of light occurs when a beam comes from the air toward the water and vice versa. Generally, refraction of light occurs when the light comes from a wide apart medium toward the closer medium and vice versa. Snellius law, in relation with light refraction, states that: 1. The coming ray, the refraction ray, and the normal line are intersecting at one point and on a flat surface. 2. The relationship among the coming angle and the refraction angle is stated as follow. 2 2 1 1 sin sin n n Where: 1 n The refraction index of medium 1
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Refraction of Light Through Plan Parallel Glass_Dana Santika_Physics_Undiksha
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1
REFRACTION OF LIGHT
THROUGH PLAN PARALLEL GLASS
A. PURPOSE OF EXPERIMENT
There are some purposes which want to be achieved from this experiment.
1. Determining the value of the index of refraction of plan parallel glass.
2. Determining the value of the shift between the coming light and light of
refraction out of plan parallel glass.
B. TOOLS AND MATERIALS
Here are the tools and materials needed in order to do this experiment.
1. Box of Light (Ray Box)
2. Protractor (SSN = 1o)
3. Plan Parallel Glass
4. Pencil
5. Ruler (SSN = 0.1 cm)
6. HVS Paper (White Paper)
C. FUNDAMENTAL THEORY
Refraction of light is a phenomenon of the light propagation direction
changing since the light passes the two different mediums. The refraction of
light occurs when a beam comes from the air toward the water and vice versa.
Generally, refraction of light occurs when the light comes from a wide apart
medium toward the closer medium and vice versa. Snellius law, in relation
with light refraction, states that:
1. The coming ray, the refraction ray, and the normal line are intersecting at
one point and on a flat surface.
2. The relationship among the coming angle and the refraction angle is stated
as follow.
2211 sinsin nn
Where:
1n The refraction index of medium 1
2
2n The refraction index of medium 2
1 The coming angle
2 The refraction angle
A beam which travels from a small density medium toward the bigger density
medium will be refracted close to the normal line, then the coming angle
would be bigger than the refraction angle. In contrary, if a beam travels from a
big density medium toward the smaller density medium, it will be refracted
avoiding the normal line, then the coming angle would be smaller than the
refraction angle. If a coming ray from the air passes the plan parallel glass as
shown by figure 1, the direction of coming ray would be parallel with the
direction of refraction ray, but it shifted as t. The value of t can be determined
by the following equation.
r
ridt
cos
sin
Where:
t = the displacement of ray
d = the thickness of plan parallel glass
i = coming angle
r = refraction angle
Figure 1. The scheme of light refraction through plan parallel glass
d
N
A
B
t
D
i
r
i r
C
d
3
D. EXPERIMENT METHOD
The following are the experiment method that should be done in order to do
this experiment.
1. Setting up the tools and materials as the following picture.
2. Measuring the thickness of plan parallel glass by ruler.
3. Drawing lines with angle 10°, 25°, 40°, 55°, and 70° with axis line PQ on
the paper.
4. Setting the position of ray box to make the coming ray exactly on the line
drawn at 10° through PQ. Then, the angle of coming ray is 10°.
5. Investigating the refraction ray and marking its direction by a cross mark
at diffraction ray. Getting up the plan parallel glass, and then drawing the
refraction ray. Where, it will be gotten two angles of refraction, there are r1
(the angle of refraction for the air-glass refraction) and r2 (the angle of
refraction for the glass-air refraction). Noting the recorded data in
providing table.
6. Repeating the steps 4 and 5 for other coming angles.
7. Recording the result data in following table.
The thickness of glass (d) =…………
No Coming ray (i1) Refraction ray 1
(r1)
Refraction ray 2
(r2)
1
2
…..
Ray Box
Plan Parallel Glass
To the source of voltage
HVS Paper
P
Q
4
E. DATA ANALYSIS TECHNIQUE
The following are the analysis technique used in order to analysis the data
recorded from the experiment.
1. Determining the refraction index of plan parallel glass (n2).
2211 sinsin nn
Where:
1n The refraction index of medium 1 (air)
2n The refraction index of medium 2 (glass)
1 The coming angle
2 The refraction angle
2. Determining the value of n of the refraction index of plan parallel glass.
yy
xx
yn
2
1
3. Stating the refraction index of plan parallel glass in the following form.
n = n n
4. Determining the relative error (RE) of refraction index of plan parallel
glass.
%100
n
nRE
5. Determining the value of the displacement of coming ray and refraction
ray that travel out the glass (t).
r
ridt
cos
sin
Where:
t = the displacement of ray
d = the thickness of plan parallel glass
i = coming angle
r = refraction angle
5
6. Determining the value of t of the displacement of coming ray and
refraction ray that travel out the glass.
dyy
dxx
y
dd
y
xt
2
7. Stating the refraction index of plan parallel glass in the following form.
t = t t
8. Determining the relative error (RE) of displacement.